As an evolved version of LTE, LTE-A is intended to meet a higher demand and more applications in the wireless communication market over the next few years, to meet and surpass a demand of International Mobile Telecommunications-Advanced (IMT-Advanced), and meanwhile to keep a better backward compatibility to LTE.
To meet the demand of IMT-Advanced, a Carriers Aggregation (CA) technology is adopted in LTE-A to further support a wider communication bandwidth than that of LTE. The main principle of the CA is that a maximum bandwidth of 100 MHz can be supported by aggregating multiple carriers which are backward compatible to LTE. The CA includes two application scenarios: Inter-band CA and Intra-band CA.
In a system where the CA is introduced, a carrier which is aggregated is referred to as a Component Carrier (CC), and also as a Cell. Furthermore, concepts of a Primary Component Carrier/Cell (PCC/PCell) and a Secondary Component Carrier/Cell (SCC/SCell) are proposed. In a system where carriers are aggregated, there are at least one PCC/PCell and one SCC/SCell, wherein the PCC/PCell is always at the activated state.
When the CA is an Inter-band CA, a User Equipment (UE) has multiple Power Amplifiers (PAs) to support simultaneous transmissions of user uplink signals on multiple CCs located on multiple frequency bands, at this point, uplink signals on each CC are sent by pre-configured PAs.
In an Intra-band CA scenario, when uplink signals on multiple CCs are sent simultaneously, if the total transmission power of the uplink signals on the multiple CCs exceeds a maximum linear power supported by a PA, a power reduction is performed on all the uplink signals, to ensure that the sum of transmission powers of all the uplink signals does not exceed the maximum linear power supported by the PA.
However, in an Inter-band CA scenario, since a UE has multiple PAs, and uplink signals on a specific CC are sent by a pre-configured PA, an evolved Node B (eNB) configures a maximum transmission power of a CC carried by the PA according to the capability of the PA, this may result in the case that a total transmission power of uplink signals on one or more PAs exceeds the maximum linear power of the PA and a power reduction is needed, while a total power of uplink signals on other PAs does not exceed the maximum linear power of the PA and a power reduction is not needed.
The power reduction formula, in TS 36.213 Release 10 of the current LTE standard, is established based on an Intra-band CA scenario. If a power reduction in an Inter-band CA scenario is performed according to the power reduction formula in TS 36.213 Release 10, transmission powers of uplink signals carried by CCs, on which a power reduction does not have to performed, will be reduced, thus lowering covering capabilities and reliabilities of uplink signals, whilst lowering a utilization rate of a UE's uplink transmission power.